This application is based upon, claims the benefit of priority of, and incorporates by reference the contents of prior Japanese Patent Application No. 2001-324993 filed on Oct. 23, 2001.
1. Field of the Invention
The present invention relates to an electromagnetic valve apparatus that generates a magnetic attractive force between a stationary core and a movable core. The electromagnetic valve controls a flow rate in a flow passage by means of a valve member which is driven to concurrently reciprocate with the movable core.
2. Description of the Related Art
Generally, it is known that an electromagnetic valve apparatus has a stationary core constructed of a housing portion and an attracting portion that are provided independently of each other. The housing portion accommodates a movable core so that the movable core can reciprocate, and so that the attracting portion can attract the movable core in one of the reciprocating directions. With this construction, there is a possibility that the axes of the housing and attracting portions may deviate from each other due to assembly errors or other reasons. To prevent interference with the reciprocating motion of the movable core due to the axial deviation between the housing and attracting portions, an air gap formed between the housing portion and the movable core, as well as that formed between the attracting portion and the movable core in the radial direction, is made large in consideration of the axial deviation. Increasing the size of the air gap entails a decrease in magnetic attractive force for attracting the movable core to the attracting portion. Therefore, a larger number of coil windings is required to obtain a magnetic attractive force of a desired level. Increasing the number of coil windings, however, requires that the electromagnetic valve apparatus have an unduly large actuator.
An electromagnetic valve apparatus disclosed in Japanese National Publication No. Hei. 11-500509 succeeds in preventing an axial deviation between an attracting portion and a housing portion by forming the attracting and housing portions of a stationary core in one piece. To attract the movable core toward one of its reciprocating directions, the attracting portion has a portion formed so as to face the movable core, i.e., a portion formed so as to be located on an inner peripheral side thereof relative to an inner wall of the housing portion. In the case of forming the attracting and housing portions integrally with each other, one end of the housing portion opposite to the attracting portion opens for convenience in processing.
However, when a valve member, which reciprocates concurrently with the movable core, is driven to control a flow rate of fluid flowing through a flow passage, there is a possibility that fluid will leak from the valve member to the movable core location. To prevent fluid leaking from the valve member to the movable core from escaping outside of the electromagnetic valve apparatus, the opening of the housing portion needs to be sealed with an additionally provided member.
It is therefore an object of the present invention to provide an electromagnetic valve apparatus in which leakage of fluid can be prevented by using a simple structure. Another object of the present invention is to provide an electromagnetic valve apparatus that is capable of maintaining a smooth reciprocating motion of its movable core.
According to the first to fourth aspects of the present invention, the electromagnetic valve apparatus is configured such that the stationary core, which accommodates the reciprocal movable core, is formed in the shape of a cup having a bottom. This eliminates the need to prepare a sealing member for preventing fluid, which may leak from the valve member to the movable core, from leaking out of the stationary core.
Moreover, the stationary core has, on its inner wall located on the opened side relative to the movable core, an attracting member placed face to face with the movable core along the reciprocating direction (path), so that a magnetic attractive force is exerted between the attracting member and the movable core. This makes it possible to secure an adequate magnetic attractive force for attracting the movable core.
According to the second aspect of the invention, the electromagnetic valve apparatus is configured such that, on the open side of the housing portion for accommodating the reciprocally movable core, a concavity is formed that is larger than the housing portion, in inner diameter, and receives therein the attracting member. The attracting member is retained by the stepped portion formed on the housing portion side of the concavity. This facilitates positioning for placing the attracting member in the stationary core.
According to the third aspect of the invention, the electromagnetic valve apparatus is configured such that, at least in one of the reciprocating directions of the movable core, a concavity for holding foreign matter is formed on the inner wall of the stationary core but located in a region outside of the range of the reciprocating motion of the movable core. Alternatively, the concavity may be formed between the inner wall of the stationary core and the outer wall of the attracting member. Foreign matter in the fluid will become trapped in the concavity and will not interfere with the sliding surfaces between the movable core and the stationary core. Therefore, the movable core will reciprocate smoothly.
According to a fifth aspect of the invention, the electromagnetic valve apparatus supplies a working fluid to a valve timing adjustment apparatus, or performs switching of a flow passage for discharging the working fluid out of the valve timing adjustment apparatus. In this case, since the stationary core exterior portion of the electromagnetic valve apparatus is surrounded by the atmosphere, it is necessary to prevent the working fluid from leaking outside of the electromagnetic valve apparatus. Therefore, by employing the electromagnetic valve apparatus embodying the present invention, the leakage of fluid to the outside of the electromagnetic valve apparatus can be prevented in a simple structure.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.